The invention relates to a high-pressure cleaning device comprising a high-pressure pump which pumps cleaning liquid out of a suction line into a pressure line leading to a discharge device, a bypass line leading from the pressure line to the suction line, a valve body closing the outlet opening between pressure line and bypass line, an actuating element for the valve body which is movable against the valve body contrary to the action of a spring into a position displacing the valve body into the open position, and an operating cylinder which is divided into two chambers by a piston sealingly displaceable in the cylinder and coupled to the actuating element, one of these chambers being arranged between the outlet opening and the bypass line and the other of these chambers communicating with the pressure line via a control line.
A high-pressure cleaning device of this type is known, for example, from DE-PS 31 24 944. With the control described therein it is possible to open the bypass line such that with a decrease in the cross section of the pressure line some of the liquid conveyed by the high-pressure pump is supplied to the suction side of the pump via the bypass line so that the amount of liquid which exits from the pressure line when this has a reduced outlet cross section is diminished. When the pressure line is closed, the bypass line is completely opened. In order, for this purpose, to be able to open the actuating element contrary to the action of the retaining spring, the pressure in the pressure line and in the control line branching of this line must rise to such an extent that it is above the pressure which occurs during normal operation. Only then can the force of the return spring be overcome and this force cannot be selected to be any less since, otherwise, the bypass line would be opened during normal operation in an undesired manner. A complete release of the bypass line therefore presupposes a pressure in the pressure line which is higher than during normal operation. Such an increase in pressure will put an exceptionally heavy strain on the electromotor of the high-pressure pump, i.e. it is necessary to dimension the electromotor such that it is also suitable for this overpressure operation. This means that the motors are required to be larger and more powerful than would be necessary as such for normal, continuous operation.